This invention is in the field of dental tools and particularly dental drills.
As generally practiced at the present time removable drills are fixed in the rotors of high speed turbines by means of screw chucks or the like. Recently a device was proposed for applying resilient inward pressure to the drill to hold it in the rotor by friction, thus eliminating the need for screws and making it possible to insert the drill shank by simply pushing it axially without having to stop the rotor. A slotted sleeve was axially compressed by a helical spring or a body of rubber extending around the same but such devices applied maximum pressure only at a limited region intermediate the end of the drill shank, thus inducing excessive wear in that region and rendering it difficult to insert or remove a drill. The pressure necessary to insert the drill axially into those devices created the risk of breaking tungsten carbide drills or bending of diamond charged drills which are long and thin.